The invention relates to a method of making groups (particularly rows) of sewn patterns in zig-zag sewing machines, and to groups (particularly rows) of patterns which are obtained in accordance with the method.
U.S. Pat. No. 4,561,369 to Meier discloses a sewn pattern arrangement which is produced by a zig-zag sewing machine. Each pattern occupies a substantially square area having a length less than the maximum bight range and a width corresponding to the maximum range in the feed direction. Each pattern has sections which extend diagonally of a portion of the respective area. The patent teaches that the width of the rectangular area for each pattern be an integer fraction of the maximum bight width and proposes to have the starting needle penetration point for the making of a next-following pattern coincide with the final needle penetration point of the preceding pattern, i.e., to avoid the making of so-called jump stitches between successive elementary patterns. Each next-following pattern can be formed above, below, laterally adjacent or diagonally of the preceding pattern. The last thread leg of each elementary pattern extends the full length of a diagonal of the respective pattern. Such patterns can be assembled into large-area arrays by grouping rows of elementary patterns side by side.
As a rule, the maximum bight range of a household sewing machine is between 5 and 8 mm, and the maximum range in the feed direction is between 4 to 6 mm, depending upon the design or setting of the mechanism which includes the feed dog. Thus, if the bight range is 8 mm and the range in the feed direction is 6 mm, and assuming that the sewing of patterns in accordance with the teaching of Meier is based on bisection of the bight width, the maximum square area which is available for the making of an elementary pattern is 4.times.4 mm, and the maximum square area available upon trisection of the bight width is approximately 2.7.times.2.7 mm. This results in the making of relatively small elementary patterns which are often unacceptable for a number of reasons.
Meier proposes to make various elementary patterns by resorting to different sequences of stitches in each of the patterns, mainly for the purpose of ensuring that a preceding pattern can end in a selected corner of the square area occupied by such pattern, namely in a corner where the making of the next elementary pattern is to begin. Such prerequisite must be met under any and all circumstances if two or more elementary patterns are to be made without jump stitches. Certain elementary patterns must have as many as three needle penetration points at the center of the cruciform pattern (note FIG. 14 of Meier). Each such penetration point at the center of an elementary cruciform pattern entails an interruption of a thread leg, i.e., it is necessary to make two shorter thread legs in lieu of a single thread leg extending all the way between two diagonally opposite corners of the square area which is taken up by an elementary pattern. The number of long thread legs is reduced proportionally with increasing number of needle penetration points at the center of an elementary pattern. Differences in numbers of long thread legs forming part of discrete elementary patterns adversely affect the appearance of an array of two or more elementary patterns. Such differences are more readily apparent if the areas of elementary patterns are relatively large, e.g., if each elementary pattern occupies a square area having sides of a length matching half the maximum bight range.